CA2805687A1 - Composition in the form of an emulsion, comprising a hydrophobic phase dispersed in an aqueous phase - Google Patents

Abstract

The present invention relates to a composition in the form of an emulsion, advantageously a Pickering emulsion, comprising a hydrophobic phase dispersed in an aqueous phase, which composition contains emulsifying particles capable of stabilizing said emulsion, at least some of said particles consisting of cellulose nanocrystals having an elongated shape, which have the following features: a length between 25 nm ant 1 µm, and a width between 5 and 30 nm.

Description

COMPOSITION IN THE FORM OF EMULSION, COMPRISING A HYDROPHOBIC PHASE
DISPERSEE IN AQUEOUS PHASE

The present invention relates to a composition in the form of an emulsion, comprising a hydrophobic phase dispersed in an aqueous phase.
STATE OF THE ART
An emulsion is of the oil-in-water type when (i) the dispersing phase is a aqueous phase and (ii) the dispersed phase is an organic phase (hydrophobic or oily).
Such an emulsion is still commonly referred to as O / W.
However, this physical state of emulsion is not stable: the organic phase has tendency to group together to form a single continuous unit, particularly because of its difference density relative to the aqueous phase.
To achieve this stability, a first approach is to use compounds so-called stabilizer, conferring on the emulsion suitable rheological properties to slow down phenomenon of coalescence.
Another way to stabilize emulsions is to use compounds so-called emulsifier or emulsifiers.
These emulsifying compounds are most often surfactants emulsifiers (still called surfactants) which, thanks to their amphiphilic structure, place to the oil / water interfaces and stabilize dispersed organic droplets.
However, emulsifying compounds of this kind do not always offer the stability sought after in time. In addition, synthetic surfactants often present disadvantages on the ecological level.
These emulsifying / emulsifying compounds may also consist of solid particles, which make it possible to obtain emulsions known as emulsions from Pickering.
Pickering emulsions are emulsions without surfactants.
assets, and are stabilized by particles in colloidal suspension coming to anchor at the interface oil / water.
Unlike surfactants that adsorb and desorb continually, the particles in colloidal suspension adsorb strongly to the interfaces (or even irreversibly).
These Pickering emulsions in practice have very good properties.
original and interesting, especially in comparison with conventional emulsions stabilized by surfactants.
In particular, it is possible to manufacture emulsions very easily, going from micrometer per centimeter, exploiting in particular the so-called coalescence limited. In addition, the compositions obtained are much more stable than their homologs stabilized by surfactants.

PCT / EU2011 / 051,717 To illustrate such a Pickering emulsion, mention may for example be made of document FR-

2,794,466 which describes the use of cellulose fibrils in cosmetic compositions of the type O / W emulsions, to ensure the stabilization of the latter in the absence of any agent surfactant.
The cellulose fibrils used have a length greater than 1 μm and preferably ranging from 5 to 40 μm, for a diameter of between 2 and 100 manometers. They have a length / diameter ratio equal to or greater than 30.
In addition, the cellulose fibrils used are in a form partially amorphous:
they preferably have a degree of crystallinity of less than or equal to 50 %, and preferably between 15 to 50%.
However, it turns out that such cellulose fibrils of greater length at 1 lm not allow to obtain calibrated emulsions of controlled size and homogeneous, and therefore do not allow the feasibility of monodisperse emulsions with sizes of reduced organic droplets. In fact, with these cellulose fibrils of a length greater than 1 μm, the stabilizing effect of an emulsion is effected by network formation entangled fibrils at the water / oil interface, which generates emulsions including large drops that are found in the form of a plurality aggregates of drops in suspension. The resulting emulsions are not homogeneous.

SUMMARY OF THE INVENTION
The objective of the invention is to propose new compositions of the kind emulsion oil in water (advantageously from the family of Pickering emulsions), containing emulsifying particles capable of stabilizing the emulsion, advantageously without surfactant and this in a particularly stable manner in time.
The present invention thus relates to a composition in the form of an emulsion comprising a hydrophobic phase dispersed in an aqueous phase, which composition contains emulsifying particles consisting of nanocrystals of shape cellulose elongated, advantageously still of acicular form, having a length range between 25 nm and 1 μm, and a width between 5 and 30 nm.
Cellulose nanocrystals have been the subject of numerous studies, in particular in sight to characterize their morphology and their crystalline structure.
However, to the knowledge of the inventors, such cellulose nanocrystals have have never been used as emulsifier / emulsifier compounds for the stabilization of emulsions.Or, as demonstrated in the following examples, such composition turns out particularly stable over time, although free of surfactants. This emulsion resists in addition to heat treatments, both freezing and heating type.
Other advantageous features that can be taken in combination or independently of each other, are detailed below:

PCT / EU2011 / 051,717

3 the cellulose nanocrystals satisfy the following characteristics:
length included between 100 nm and 11 μm, and a width between 5 and 20 nm;
the cellulose nanocrystals have a length / width ratio greater than 1 and less than 100, and preferably between 10 and 55;
the cellulose nanocrystals have a maximum surface charge density 0.5 e.nrn-2, and preferably a maximum surface charge density of 0.31 e.nrn-2, e corresponding at an elementary charge; according to a first embodiment, the cellulose nanocrystals comprise a charged surface, advantageously surface charges negative, with a surface charge density of between 0.01 e.nrn-2 and 0.31 e.nrn-2;
according to a second embodiment, the cellulose nanocrystals have a neutral surface, the charge density the surface area being less than or equal to 0.01 e.nrn-2;
the cellulose nanocrystals comprise, on the surface, groups hydrophobic.
The present invention also relates to the use of nanocrystals of cellulose such as defined above, to stabilize an emulsion comprising a phase hydrophobic dispersed in an aqueous phase.
The invention also relates to the process for the manufacture of a composition under emulsion form defined above, comprising the following steps:
(a) the supply of cellulose nanocrystals as defined above, then (b) incorporating said cellulose nanocrystals into the aqueous phase of said composition, so as to stabilize said emulsion.
The cellulose nanocrystals provided in step (a) are advantageously obtained by a method of manufacturing from a cellulose, said method of manufacturing being chosen from one of the following processes: mechanical fractionation, chemical hydrolysis arranged, and dissolution / recrystallization In this case, the process for producing the cellulose nanocrystals is advantageously followed by a method of post-modification of said nanocrystals from cellulose to after which their density of surface charges and / or their hydrophobicity are modified.
For a change in charge density, the post-modification process is advantageously in a process for introducing or hydrolyzing the groups bearing the surface charges, which groups are preferably chosen from groups sulfonate, carboxylate, phosphate, phosphonate and sulfate.
According to a first preferred embodiment, the manufacturing method consists of a process for the controlled acid hydrolysis of cellulose with sulfuric acid, for get some cellulose nanocrystals with sulfate groups on the surface; and the post-process optional modification consists of a controlled hydrolysis process of the said groups sulfate.
According to a second preferred embodiment, the manufacturing method consists of a method of controlled acid hydrolysis of cellulose with hydrochloric acid;
and the method of

4 optional post-modification consists of a process of post-sulphation of said nanocrystals of cellulose.

DETAILED DESCRIPTION OF THE INVENTION
Composition according to the invention As mentioned above, the composition according to the invention consists of composition under form of an emulsion comprising a hydrophobic phase dispersed in a phase aqueous, and containing emulsifying particles (or in other words particles emulsifiers) consisting of cellulose nanocrystals.
Emulsion means a mixture, macroscopically homogeneous but microscopically heterogeneous, of two immiscible liquid phases.
In this case, the emulsion according to the invention is of the oil-in-water type, that is to say that (i) the dispersing phase is an aqueous phase and (ii) the dispersed phase is a phase organic (hydrophobic or oily). Such an emulsion is still designated commonly by the acronym H / E.
To ensure its stability, the emulsion according to the invention thus contains nanocrystals of cellulose.
Cellulose nanocrystals are known from the prior art, often under the denomination of cellulose whiskers or cellulose nanowiskers.
Such nanocrystals of cellulose can come from various sources:
vegetable (eg wood pulp, cotton or algae), animal (eg tunicate), bacterial, regenerated cellulose or mercerized cellulose. They are for example described in the document Samir and al. (2005, Biomacromolecules, Vol.6: 612-626) or in the document Elazzouzi-Hafraoui and al.
(Biomacromolecules, 2008, 9 (1): 57-65.).
More specifically, cellulose nanocrystals are solid particles highly crystal.
These cellulose nanocrystals are lacking, or at least practically deprived of amorphous part. They preferably have a degree of crystallinity of from minus 60%, and preferably between 60% and 95% (see for example Elazzouzi-Hafraoui and al., 2008 supra).
For the composition according to the invention, the cellulose nanocrystals have a form length, that is to say advantageously a length / width ratio greater than 1.
More preferably, these cellulose nanocrystals have an acicular form, that is say a linear and pointed shape reminiscent of a needle.
This morphology can be observed for example by electron microscopy, in particularly by transmission electron microscopy (or TEM).

5 Still in the composition according to the invention, these cellulose nanocrystals behave the following dimensional characteristics: (i) a length between 25 nm and 1 jim, and (ii) a width of between 5 and 30 nm.
By length, we mean the largest dimension of nanocrystals, separating two points at the ends of their respective longitudinal axis.
By width, we mean the dimension measured along the nanocrystals, perpendicular to their respective longitudinal axis and corresponding to their maximum section.
In preferred embodiments, the cellulose nanoparticles form a relatively homogeneous population of nanocrystals whose values experimental length follow a Gaussian distribution centered on the length value assigned for said population of nanocrystals. In these preferred embodiments, can use by cellulose nanocrystals of one specific size, such as that is illustrated in the examples.
In practice, the morphology and dimensions of the nanocrystals can be determined using different imaging techniques like the electron microscopy transmission (MET) or atomic force microscopy (AFM), the diffusion of X-rays or small angle neutrons (respectively SAXS for Small-Angle X-ray Scattering and NO for Small-Angle Neutron Scattering) or dynamic diffusion light (D DL).
According to a preferred embodiment, the cellulose nanocrystals exhibit the following dimensions: (i) a length of between 100 nm and 1 μm, and (ii) a width between 5 and 20 nm.
Advantageously, the cellulose nanocrystals have a relationship length Width greater than 1 and less than 100, preferably between 10 and 55.
A length / width ratio greater than 1 and less than 100 includes reports length / width of at least 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98 and 99.
A length / width ratio of 10 to 55 includes the ratios length / width selected from 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53 and 54.
For example, nanocrystals obtained from cotton cellulose behave advantageously a length of between 100 nm and 200 nm, for a width range between 12 and 15 nm. The length / width ratio is advantageously included between 7 and 17, and preferably between 10 and 13.

PCT / EU2011 / 051,717

6 In another example, the nanocrystals can be obtained from a cellulose bacterial. Such nanocrystals (known as nanocrystals of cellulose bacterial or BON) advantageously comprise a length included between 600 nm and 11m, for a width between 12 and 17 nm. The report length / width is included advantageously between 35 and 83, preferably between 45 and 55.
To optimize the stability of Pickering emulsions, nanocrystals from cellulose are advantageously chosen according to their surface characteristics, taking into account including (i) the electrostatic appearance and / or (ii) the hydrophobicity or hydrophilicity.
Concerning the surface electrostatic aspect, cellulose nanocrystals stabilizing the emulsion advantageously have a maximum surface charge density of 0.5 e.nrn-2, and preferably a maximum surface charge density of 0.31 e.nrn-2. We note that e corresponds to an elementary charge.
The surface charge density and the ionic strength of the aqueous phase are advantageously adapted to each other.
Advantageously, this surface charge density is determined by assaying conductimetric; a particular embodiment is described below in the part Examples.
More precisely and according to one embodiment, the nanocrystals of cellulose have a loaded surface, with a density of surface charges between 0.01 e.nrn-2 and 0.31 e.nrn-2.
As described in the examples, the desired density of charges of surface can be obtained by a control of the degree of sulfation of the nanocrystals. The degree of sulfation nanocrystals can be controlled by subjecting the nanocrystals of cellulose to a treatment sulfation and, if necessary, subsequent desulfation treatment.
The applicant has shown that a stable Pickering emulsion is obtained when uses substantially uncharged cellulose nanocrystals.
The Applicant has also shown that beyond 0.31 e.mm-2, the stability of the Pickering emulsion is very significantly altered. The plaintiff shown that cellulose nanocrystals having a charge density value too large present a surface too hydrophilic and are found in large quantities in suspension in the phase rather than being located at the oil / water interface to stabilize the emulsion.
In this case, the cellulose nanocrystals advantageously comprise loads negative surface areas, which are advantageously carried by groups anionic surface.The anionic groups of cellulose nanocrystals are chosen for example among the sulphonate groups, the carboxylate groups, the groups phosphate, phosphonate groups and sulfate groups.
The transposition of a degree of substitution value (DS) to the value corresponding density of surface charges (e.mm-2) is direct, as long as the number loads of PCT / EU2011 / 051,717 considered chemical group is known. For illustrative purposes, for sulfate groups, which carry a single charge, the value of DS (number of sulfate groups per surface unit) is identical to the surface charge density value (number of charges per unit of identical surface).
In other words, these cellulose nanocrystals have a degree of substitution (DS) between 10-3 and 10-2 e / nm2, or a degree of surface substitution (DSs) between DS / 0.19 to DS / 0.4, depending on the morphology of the nanocrystals used.
According to another embodiment, the cellulose nanocrystals have a area neutral. In this case, the density of surface charges is advantageously less than or equal at 0.01 e.nrn-2.
In practice, the charge density of the cellulose nanocrystals is advantageously chosen according to the ionic strength of the aqueous phase of the composition.
The cellulose nanocrystals used according to the invention consist advantageously in cellulose nanocrystals that have not been treated hydrophobizing. This encompasses cellulose nanocrystals whose hydroxyl groups have not been functionalized by atoms or hydrophobic groups. Typically, this includes nanocrystals who have not not undergone hydrophobization treatment by esterification of groups hydroxyl by organic acids.
In advantageous embodiments, the cellulose nanocrystals which are used to obtain the Pickering emulsion do not undergo any treatment posterior chemical to obtain them, other than a desulfation or sulphation treatment.
In particular, we use preferentially cellulose nanocrystals which have not been functionalized or grafted with groups allowing their subsequent crosslinking, for example by groups of methacrylate or dimethacrylate type. Also, preferentially used nanocrystals of cellulose which have not been functionalized or grafted by molecules polymers, such polyethylene glycol, poly (hydroxyester) or polystyrene.
The Applicant has also shown that the stability of the Pickering emulsion can be increased by using an aqueous phase with minimal ionic strength determined.
In this case, maximum stability of the Pickering emulsion is obtained for a ionic strength value corresponding to a final concentration of NaCl of 0.02 M in said emulsion.
Without wishing to be bound by any theory, the Applicant believes that the threshold value ionic strength of the aqueous phase from which a stability optimal emulsion is obtained for which the charges (counter-ions) present in the aqueous phase neutralize the charges (ions) present on the nanocrystals.
As shown in the examples, the presence of excess counterions no influence not significantly on the stability properties of the emulsion. For a massive excess of counter-ions, which has not been reached under the operating conditions of the examples, we can presage an alteration of the stability of the emulsion, due to precipitation of nanocrystals.

PCT / EU2011 / 051,717 As an indication, according to a particular embodiment, for a composition having an ionic strength lower than the ionic strength equivalent to 10 mM
NaCI, the cellulose nanocrystals advantageously comprise a charge density of area maximum of 0.03 e.nrn-2.For a composition comprising an ionic strength greater than the ionic strength equivalent to 10 mM NaCl, the surface charge density carried by the nanocrystals of cellulose appears to no longer be a relevant parameter for stabilization effective the emulsion.
An ionic strength greater than the ionic strength equivalent to 10 mM NaCl includes a ionic strength greater than 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 210, 220, 230, 240, 250, 260, 270, 275, 280, 290, 300, 310, 315, 320, 325, 330, 335, 340, 345, 350, 360, 370, 375, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, or greater than 500 mM NaCl. Preferably, the ionic strength is less than an ionic strength equivalent to 3 M NaCl.
The results of the examples show that in some embodiments a according to the invention, the stability of said emulsions is already maximal for a force ionic composition of 20 mM NaCl, and the level of stability of the emulsion being maintained virtually unchanged for all ionic strength values tested, that is to say at least up to an ionic strength value equivalent to the ionic strength of 0.5 M NaCl.
In an alternative or complementary way, always to optimize the stabilization of emulsions, the cellulose nanocrystals comprise groups hydrophobic area.
The density of hydrophobic groups at the surface can be a parameter interesting to account for interfacial tension (nature of the aqueous phase and the sentence oily).
Such hydrophobic groups are advantageously chosen from acetyl, alkyl, aryl, phenyl, benzyl, hydroxybutyl groups, hydroxypropyl polycaprolactone (or PCL).
Cellulose nanocrystals are usually incorporated into the phase aqueous the composition.
According to a preferred embodiment, the Pickering emulsion composition is stabilized only by cellulose nanocrystals, without the addition of other compounds emulsifier or stabilizer.
According to a preferred embodiment, the Pickering emulsion composition born includes no solid, non-functionalized or functionalized particles, other than cellulose nanocrystals.

PCT / EU2011 / 051,717 Alternatively, the composition is stabilized by the nanocrystals of cellulose, reported in combination with at least one other compound having properties emulsifying and / or stabilizing properties, for example with or without surfactant (s).
active (s).

For example, the Pickering composition according to the invention may contain CTAB

(hexadecyltrimethylammonium bromide).

The composition advantageously comprises from 0.035% to 2% by weight, preferably from 0.05% to 1% by weight of cellulose nanocrystals relative to total weight of said composition.

This mass proportion of cellulose nanocrystals can be evaluated by example by dry extract of the aqueous phase or by assaying the sugars after hydrolysis.

It is shown according to the invention that a quantity of cellulose nanocrystals sufficient to obtain a recovery rate of at least 60% is preferred for the preparation of a Pickering emulsion composition.

In particular, when a mass of nanoparticles that is too weak is used by volume ratio of oil, it is likely to coalesce droplets of the sentence hydrophobic so as to tend to a minimum coverage of 60%.

For the purposes of this description, the recovery rate for nanocrystals of cellulose represents the proportion of the surface of the phase droplets hydrophobic dispersed in the aqueous phase, at the oil / water interface, which is covered by the cellulose nanocrystals.

The recovery rate C, which is the ratio between (i) the area of nanocrystals of cellulose present in the emulsion composition capable of stabilizing at the interface hydrophobic internal phase / hydrophilic continuous phase and (ii) the total area droplets of hydrophobic phase in said emulsion composition is calculated according to the following formula (I):

C = Sp / Sd (I), wherein:

- S. represents the surface of nanocrystals of cellulose likely to stabilize at the interface present in the emulsion composition, and Sd represents the total area of the hydrophobic phase droplets in the composition emulsion.

The surface of the nanocrystals is assimilated to a single-plane surface, in taking the hypothesis that the nanocrystals are aligned on said surface in a ribbon dish.

As a result, the surface value of the nanocrystals can be calculated according to the following formula (II):

Sp = = NpL1 N1P, ite with. Np = mP = mP
Vpxpp Lxlxhxpp in which :

PCT / EU2011 / 051,717 - S. represents the surface of nanocrystals of cellulose likely to stabilize at the interface present in the emulsion composition, - Np means the number of cellulose nanocrystals present in the phase aqueous, L is the length of the cellulose nanocrystals, - I means the width of the cellulose nanocrystals h is the height of the cellulose nanocrystals mp means the mass of cellulose nanocrystals, and p is the density of the cellulose nanocrystals The surface of the droplets is the surface at the oil / water interface, which has been calculated for each average diameter of droplets according to D (3,2).

As a result, the surface value of the droplets can be calculated according to the following formula (III):
Sd = 47-i-R2xNg = 471-R2x 3170, / = 3VOil (III), with. Ng = Voi / (IV) 4/3 7e3 in which :

- Ng means the number of drops present in the emulsion Sd means the surface value of the hydrophobic phase droplets, R is the mean radius of the droplets, and V01 signifies the total volume of the hydrophobic internal phase.

The final value of the recovery rate C is calculated according to the formula (I) already mentioned above:

C = Sp / Sd (I), wherein:

- Sp represents the surface of nanocrystals of cellulose likely to stabilize at the interface and present in the emulsion composition, Sd represents the total area of the hydrophobic phase droplets in the composition emulsion.

In the Pickering emulsion composition, the hydrophobic dispersed phase advantageously represents less than 50% by volume relative to the total volume of the composition.
The hydrophobic phase advantageously represents from 5% to 45% by volume report to the total weight of the composition.

As described below, the hydrophobic phase is selected from oils plant, animal oils, mineral oils, synthetic oils, organic solvents hydrophobic and hydrophobic liquid polymers.
The Pickering emulsion composition according to the invention may further contain other compound appropriate for its use or final destination.

This Pickering emulsion composition can thus be adapted to the chosen application advantageously among the food compositions, the compositions cosmetics, pharmaceutical compositions and phytosanitary compositions.
In known manner and according to its application, the composition can contain by example, without being in any way limiting, active principles and adjuvants such as preservatives, gelling agents, solvents, dyestuffs, etc.

The hydrophobic phase The hydrophobic phase is chosen from vegetable oils, oils and animal mineral oils, synthetic oils, hydrophobic organic solvents and polymers hydrophobic liquids.
The hydrophobic phase may be chosen from an alkane or a cycloalkane, substituted or unsubstituted.
For the hydrophobic phase, an alkane having more than 5 carbon atoms includes the alkanes having more than 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or more than 17 carbon atoms, that is to say, according to the conventional nomenclature, the alkanes in C6-C18 and who are of formula C, H2n + 2. Said alkanes may be linear or branched.
Said alkanes include linear, cyclic or branched alkanes, Types hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane and octadecane.
Substituted alkanes include linear or branched alkanes above of which least one hydrogen atom is substituted with a halogen selected from chlorine, bromine, iodine or fluorine. The substitution of at least one hydrogen atom, encompasses the substitution of 2, 3, 4 or 5 hydrogen atoms.
In certain embodiments, said cycloalkane is a non-cyclohexane substituted or substituted. Cyclohexane can be substituted with 1, 2, 3 or 4 atoms chosen halogen among chlorine, bromine, iodine or fluorine.
The hydrophobic phase may further comprise a mixture of such alkanes, for example example in the form of paraffin oil.
In some embodiments, the hydrophobic phase comprises one or many polymerizable hydrophobic monomers of a known type.
In other embodiments, the hydrophobic phase consists of essentially in a composition of a hydrophobic monomer or a mixture of monomers hydrophobic. AT
As an illustration, the hydrophobic phase may consist essentially of composition of styrene monomers.

The hydrophilic phase By hydrophilic phase or aqueous phase is meant an immiscible liquid with the hydrophobic phase. A hydrophilic phase which is miscible with the water. The hydrophilic phase can be water, as illustrated in examples.
The hydrophilic phase may be a hydrophilic solvent, preferably a solvent wearing hydroxyl groups, such as glycols. For the hydrophilic phase, glycols include the glycerol and polyethylene glycols.
The hydrophilic phase may also contain water-soluble agents texturing, especially thickeners or viscosifiers, such as polysaccharides (for example dextran or xanthan, the latter being widely used in food applications).
The hydrophilic phase may consist, partly or totally, of a liquid organic selected from an alcohol such as ethanol or acetone.
The hydrophilic phase may comprise a single liquid or a mixture of several liquids.

Process for obtaining the composition according to the invention The process for the manufacture of the composition according to the invention comprises advantageously the following steps:
(a) the supply of cellulose nanocrystals as defined above, then (b) incorporating said cellulose nanocrystals into the aqueous phase of said composition, so as to stabilize said emulsion.
The general steps for the manufacture of the emulsion can be realized according to conventional procedures, especially for the manufacture of Pickering.
For example, it is possible to use a technique for obtaining emulsion by ultrasound.
In particular, the step of incorporating the cellulose nanocrystals into the phase aqueous solution corresponds to the steps implemented for the incorporation of colloidal particles during the manufacture of Pickering emulsions.
The cellulose nanocrystals provided in step (a) are advantageously obtained by a manufacturing process from a cellulose.
The cellulose is advantageously chosen from at least one of the celluloses original following: plant, animal, bacterial, algal or regenerated from a cellulose transformed from commercial sources.
The main source of cellulose is vegetable fiber. Cellulose is there present as a component of the cell wall, in the form of microbial bundles fibrils.
Part of these microfibrils is composed of so-called amorphous cellulose, so that a second part consists of so-called crystalline cellulose.
The cellulose nanocrystals are advantageously derived from cellulose crystalline isolated from plant fibers, by removing the amorphous part of cellulose.
Among the plant sources, there may be mentioned, for example, cotton, birch, hemp, ramie, flax, spruce.

Among the algal sources of cellulose, there may be mentioned for example Valonia or Chladophora.
Among the bacterial sources of cellulose, mention may be made of Gluconoacetobacter xylinus which produces Nata de coco by incubation directly in nut milk coconut.
Among the animal sources of cellulose, there may be mentioned, for example, the tunicate.
Cellulose can also be regenerated from a cellulose transformed from commercial sources, particularly in the form of paper.
For example, Whatman (trademark) filtration paper may be mentioned for obtaining cotton cellulose.
Cellulose may also consist of a so-called mercerized cellulose (the mercerization consists of a cellulose treatment usually based of hydroxide sodium).
Starting from this cellulosic raw material, the manufacturing process of nanocrystals is advantageously chosen from one of the following processes:
splitting mechanical, controlled chemical hydrolysis, and dissolution / recrystallization By mechanical fractionation is meant a conventional operation high pressure homogenization.
By controlled chemical hydrolysis is meant treatment with a compound chemical acid of cellulose, under conditions ensuring the elimination of its amorphous part.
The acidic chemical compound is advantageously chosen from sulfuric acid or hydrochloric acid.
As described in the examples below, depending on the type of acid, the temperature and hydrolysis time, the surface charge can be modulated.
Thus, hydrolysis by hydrochloric acid will lead to a surface condition nearly neutral, while hydrolysis with sulfuric acid will introduce sulphates (group S03-) on the surface of the cellulose nanocrystals.
Such type of chemical hydrolysis treatments are for example described in the document Elazzouzi-Hafraoui et al. (2008) above or in the document Eichhorn SJ and al (Review: current international research into cellulose nanofibers nanocomposites. J
Mater Sci 2010, 45, 1-33).
By dissolution / recrystallization is meant a treatment with a solvent, for example phosphoric acid, urea / NaOH, ionic liquids, etc., followed by recrystallization. Such The process is described, for example, in Helbert et al (Cellulose.
1998, 5, 113-122).
Before their incorporation into the composition, the cellulose nanocrystals obtained are advantageously subjected to a post-modification process, after which their density of surface charges and / or their hydrophobicity / hydrophilicity are modified.
This post-modification aims to optimize the surface characteristics of nanocrystals of cellulose, in particular according to the emulsion in which they are introduced, so as to optimize its stabilization.

To modify the density of surface charges, the post-process modification consists advantageously in a process for introducing or hydrolyzing groups in area carrying said surface charges.
In this case, the post-modification operation includes a step of introduction or hydrolysis of surface groups chosen from sulphonate groups, carboxylate, phosphate, phosphonate and sulfate.
As an indication, for the introduction of the respective surface groupings, We can put a process as described in Habibi Y et al. TEMPO-mediated surface oxidation of cellulose whiskers, Cellulose, 2006, 13 (6), 679-687.
Again as an indication and conversely, for the hydrolysis of such groups surface, we can carry out an acid treatment as described below in the Examples part or mechanical treatment of the sonication type.
In this context and according to a first embodiment, the method of manufacturing consists of a process for the acidic hydrolysis of cellulose by the acid sulfuric, for obtain cellulose nanocrystals with sulfate groups on the surface.
And the post-modification process consists of a hydrolysis process controlled of said sulfate groups, ie for example by acid treatment (chosen by example among hydrochloric acid or trifluoroacetic acid) for a period of time adapted to degree hydrolysis sought.
According to a second embodiment, the manufacturing process consists of a process of mild acid hydrolysis of cellulose with hydrochloric acid.
And the optional post-modification process consists of a post-modification process.
sulfation said cellulose nanocrystals. Such post-sulfation is advantageously implemented by acid treatment of the nanocrystals with sulfuric acid.
To modify hydrophobicity, the post-modification process consists of advantageously in a process for introducing or hydrolyzing groups presenting a hydrophobic character.
Among the hydrophobic groups that can be introduced or eliminated, can quote in particular the alkyl, aryl, phenyl, benzyl and acetyl groups, hydroxybutyl hydroxypropyl, polycaprolactone (or PCL).
As an indication, for the introduction and / or hydrolysis of area respective documents, reference may be made to the following documents H Lonnberg et al., Surface grafting of microfibrillated cellulose with poly (epsilon-caprolactone) - Synthesis and characterization, European polymer journal 44, 2991-2997, or R. Debashish et al.
Cellulose modification Chemical Society Reviews 2009 38 (7) 1825-2148.
The present invention is further illustrated, without being limited, by the examples presented below.

FIGURE
Figure 1 illustrates the influence of the ionic strength of the composition emulsion, on the stability of said emulsion. On the abscissa, ionic strength values, expressed in final molar concentration of NaCl of the aqueous phase. On the ordinate, the volume fraction emulsion, expressed as a percentage by volume.

EXAMPLE:
Preparation of an oil-in-water Pickering emulsion, stabilized by cellulose nanocrystals A. Protocols Protocol 1: Preparation of bacterial cellulose nanocrystals The process for obtaining the nanocrystals of bacterial cellulose is described for example in NR Gilkes et al., J of Biological Chemistry 1992, 267 (10), 6743-6749.
BON fragments are nanofibrilated in a Waring blender, at full speed, in an aqueous suspension containing ice cubes so as to combine stress from shear and impact.
The dough thus obtained is drained through polyamide filters, then suspended in 0.5 N sodium hydroxide solution with stirring in a flask closed during two hours at 70 C.
After removal of the alkaline elements through multiple rinses with some water adjusted to pH 8, a bleaching step is carried out with chlorite of so to get a a hollocellulose compound as described in Gilkes et al. (Gilkes, N.
R .; Jervis, E .;
Henrissat, B .; Tekant, B .; Miller, RC; Warren, RAJ; Kilburn, DG, The adsorption of a bacterial cellulase and its 2 isolated domains to crystalline cellulose. J.
Biol. Chem. 1992, 267 (10), 6743-6749).
Typically, a solution of NaCl2, 17 g / L, is mixed with a volume identical pH 4.5 acetate buffer (27 g of NaOH + 75 g of acetic acid per liter).
The bleached bacterial cellulose is then suspended and heated under stirring at 70 C, for two hours with reflux.
These alkaline treatment and bleaching steps are repeated at least once times, for obtaining a bleached pulp.
This bacterial cellulose is then hydrolyzed by means of a solution acid hydrochloric acid (2.5N, two hours under reflux).
The acidic compounds are removed by the successive operations up to neutrality:
centrifugation (10000g pendants minutes) and dispersion in a solution purified 18 Mohm.
The cellulose nanocrystals thus obtained are stored at 4 C in the form a suspension 1%, with addition of a drop of 0H013 per 250 mL of suspension.

Protocol 2: Preparation of post-bacterial cellulose nanocrystals sulfated An aqueous suspension of bacterial cellulose nanocrystals 1.34%, obtained according to protocol 1, is mixed with a 2.2M H2SO4 solution (ie one ratio 3/2 v / v) under vigorous stirring at room temperature.
The nanocrystals are then deposited by centrifugation (10000 g / 5 min).
The product obtained is mixed with glass beads (diameter 3 mm), then centrifugal again (10000 g / 10 min).
The glass beads coated with sulphated nanocrystals are stored at dry for two hours at 40 C.
The beads are then dried in a desiccator, in the presence of P205 at 50 C
for 14 hours.
The sulphated cellulose nanocrystals are recovered by washing the balls with the water distilled, and successive centrifugation from 10000 rpm up to 76000 rpm for 10 to 30 minutes, to obtain a colloidal suspension.
Finally, the collected product is dialyzed until neutral, and the electrolytes residuals are removed on ion exchange resin (mixed bed resin TMD-8, form hydrogen and hydroxide).

Protocol 3: Desulfation of post-bacterial cellulose nanocrystals sulfated The suspension of 2.2% post-sulfated bacterial cellulose nanocrystals according to protocol 2, is heated for three hours at 100 ° C. in 2.5N HCl, and then washed by centrifugation at 6000 rpm for 5 minutes six times.
The collected product is then dialyzed to neutrality, and the residual electrolytes are removed on an ion exchange resin (TMD-8 mixed bed resin).
Protocol 4: Preparation of Sulphated Cellulose Nanocrystals from Cotton The process for obtaining nanocrystals of cotton cellulose is described by example in the document Elazzouzi-Hafraoui et al. (2008).
25 g of paper is moistened in 700 ml of deionized water, then the solution is mixed until a homogeneous mixture is obtained. The excess water is then removed by filtration.
The product obtained is suspended in 500 mL of a sulfuric acid solution 61%, maintained at 72 C with stirring for 30 minutes.
The suspension is then cooled, washed with ultrapure water by centrifugation successive at 8000 rpm for 15 minutes, and dialyzed until neutral for three days with a reception phase consisting of distilled water.
The residual electrolytes are then extracted using a resin bed mixed (TMD-8, hydrogen and hydroxyl form) for 4 days.
The final dispersion, consisting of sulphated cotton, is stored at 4 C.

Protocol 5: Desulfation of sulfated cotton nanocrystals The desulfation of the sulphated cotton nanocrystals according to the protocol 4 is produced by acid treatment, using 5 mL of a 5N HCl solution or acid solution 10 N trifluoroacetic acid (TFA), added to 5 mL of a suspension of nanocrystals of cotton sulphated at a concentration of 13 g / L.
This acid treatment is carried out in a closed container heated to 98.degree.

with stirring, for 1, 2, 5 or 10 hours.
Alternatively, 5 mL of a 10M TFA solution is added to 5 mL of nanocrystals of cotton, with an incubation for 10 hours at 80 C with stirring.
The two products obtained were rinsed with water by centrifugation (at six times, 6000 rpm for 5-7 minutes).

Protocol 6: Measurement of sulfation degree by conductimetric titration Conductometric titration determines the degree of sulfation of cellulose nanocrystals.
Such a method is described for example in the document Goussé et al., 2002, Polymer 43, 2645-2651.
50 mL of an aqueous suspension of cellulose nanocrystals (0.1%
w / v) are kept stirring and degassing for 10 minutes, before titration with a 0.01M NaOH solution The amount of grafted sulphate is calculated taking into account that only one hydroxyl group OH may be substituted per glucose unit, leading to a degree of sulfate substitution (DS) given by the following equations:
DS = (Veq x CNaOH XM) / M
Mw = 162 / (1 - 80 x Veq x CNaoH) / m) in which Veq is the amount of NaOH in mL to reach the equivalence point, CNaOH is the concentration of NaOH expressed in mol / L, Mw is the average molecular weight of a glucose unit, m is the titrated cellulose mass, 80 is the difference between the molecular weight of a glucose unit sulphated and weight molecular weight of an unsulfated glucose unit.
The value obtained by these equations must be corrected by the fraction of unity surface glucoside (GSF), to obtain the degree of substitution in designated area DSs.
According to the structure of the cellulosic chains, only the primary OH groups (in C6) can be esterified, and only 50% of these OH groups are accessible to the surface in because of the alternating conformation. The maximum DSs is thus 0.5.

Since the samples vary in morphology and for one application general to all the different cellulosic particles, an equation general has been defined so to determine the value of surface glucose fraction (GSF) taking into account of the ratio of cross section (k) regardless of the length of the particles.
Thus, for a given width (Wx1) and an aspect ratio (k), we have:
GSF (k) = ((2 * ((k * 0.596) +0.532)) / VVxI) -4 * ((k * 0.532 * 0.596) / Wx12) Protocol 7: Transmission Electron Microscopy (TEM) 1.11_ of an aqueous suspension of cellulose nanocrystals (0.1%
w / v) are deposited on a carbon grid for electron microscopy; excess of solvent absorbed, the sample is labeled with the addition of uranyl acetate (2% in the water).
This grid for electron microscopy is then dried in an oven at 40 C.
The grids were then observed with an electron microscope in transmission JEOL brand (80kV).
Protocol 8: Preparation of an O / W Emulsion Stabilized by Nanocrystals A first Pickering oil emulsion in water is prepared using a phase aqueous solution containing a known concentration of cellulose nanocrystals.
The other emulsions were prepared using a ratio 30/70 oil / water to go an aqueous phase containing nanoparticles at a concentration of 0.5%
by weight, by relative to the weight of the emulsion (without additional dilution).
In an Eppendorf tube, 0.3 mL of hexadecane is added to 0.7 mL of the suspension aqueous; for 30 seconds, the mixture is subjected to an alternating treatment 2 seconds Ultrasound treatment and 5 seconds of rest.
Protocol 9: Stability test, optical microscopy The emulsions obtained according to protocol 8 are centrifuged for 30 minutes.
seconds to 10000 g. Given the difference in density between hexadecane and water, a creamy is observed. The emulsion volume is evaluated before and after centrifugation.
Approximately 1.11% of the Pickering solution is incorporated into 1 mL of water.
distilled. The product is mixed by vortex, then a drop is deposited on a coverslip for observation under the microscope.
The droplet diameter is measured from the images obtained by analysis images using an imageJ program,.
These results were also compared to the distribution of drops determined by a Malvern MasterSizer device employing a device to diffraction of the light with Fraunhofer equation analysis. The risk of aggregation is in this case limited by the addition of SDS (Sodium Dodecyl Sulfate) just before the measurement.

PCT / EU2011 / 051,717 Protocol 10: SEM Scanning Electron Microscopy To prepare the emulsion sample for observation by microscopy scanning electron microscope (SEM), 280-380 mg of a styrene / initiator mixture (st ratio: V-65 120: 1 w / w) are mixed with 1.0 to 1.5 mL of 0.5% solution of a solution sample of water, sonicated for 1-2 min and degassed with nitrogen for 10 minutes.
The emulsion was ultrasonically obtained for 30 seconds (pulse of 3 seconds separated by 5 seconds).
Then 500 μL of water is added to the system, then treated by vortexing.
This system is degassed with nitrogen for 10 minutes, and the polymerization had place at 63 C without agitation for 24 hours.
The resulting preparation is subjected to a metallization step according to the techniques conventional scanning electron microscopy, before observation.
For its observation by scanning electron microscopy, the sample emulsion can still be prepared with another initiator, namely the AIBN
(azobisisobutyronitrile), the following protocol:
- Degassing and stirring of 17.5 mL suspension of nanocrystals at 3 g / L 50 mM, during 10 min under nitrogen, addition of 7.5 mL of styrene and 69.8 mg of AIBN, Ultrasonic emulsification for 1min, degassing for 10min, and -polymerization with stirring at 70 C, between 1h and 24h.
The resulting preparation is subjected to a metallization step according to the techniques conventional scanning electron microscopy, before observation.
Protocol 11: Acetylation of bacterial cellulose nanocrystals 5 mL of a 1.34% bacterial cellulose nanocrystal suspension are mixed with 40 mL of 100% acetic acid solution.
The water is gradually replaced by acetic acid by distillation on a rotary evaporator (the temperature of the water bath is less than 40 C), then centrifuged at five recovery (5 minutes at 10000 g).
40 mL of the acetic acid sample is divided into two parts.
The two parts are mixed and heated at 40 C for 5 minutes and during 1 min with 6 μl of a catalyst at 5 ° C.
Then 2.5 mL of a mixture of 98% acetic anhydride and acetic 100% (in a ratio 1: 1 volume / volume) are added.
The sample solution is observed under polarized light so as to detect the presence of liquid crystals.

The reaction is stopped by adding water (ratio 1: 1 v / v), after a minute for a part (B1), after three minutes for the other part (B2).
Final ultracentrifugation (10,000 g for 10-30 minutes) of all solutions obtained allows to collect and rinse the product.
The product obtained is mixed with a mixed bed resin for three hours and then then filtered.

Protocol 12: Acetylation of cotton cellulose nanocrystals mL of 2.4% suspension by weight of desulfated cotton nanoparticles (see Protocol 5 - the nanoparticles were desulfated by 2.5 N HCl 3 h) are mixed with 90 mL of 100% acetic acid.
The water is progressively replaced by acetic acid by distillation on a rotary evaporator (the temperature of the water bath was below 40 C), then centrifugation 5 times 7min to 10000g.
80 mL of sample volume in acetic acid are divided into 2 fractions.

First method The two fractions were heated at 60 ° C. with 190 μl of catalyst, to know a sulfuric acid solution at 5% by weight in acetic acid, and stirred.
After 5 minutes, 5 mL of a mixture consisting of 98% acetic anhydride and acid 100% acetic acid, in a ratio 1: 1 v / v, are added; and the solution of the sample was put under observation in polarized light to observe the behavior of liquid crystal the sample.
When the transformation into liquid crystals is observed, the reaction is stopped by cooling in an ice-water bath; 10 mL of 80% acetic acid is in more versed in the balloon and then water, which is half the volume of the solution of the sample.
The reaction is stopped after 1.5 min for the first fraction, and after 0.5 min for the second.
Finally, ultracentrifugation (65000 rpm for 15-30min) of the solution second sample obtained is made to collect and rinse the products;
electrolytes residuals are removed by ion exchange resin for 3 hours before the filtration.

Second method Part of the sample (c-wh 3) is heated to 40 C with stirring, for 5 minutes and then after 1 min with 190 L of 5% catalyst (see above).
Then 5 mL of a mixture consisting of 98% acetic anhydride and acetic to 100/0 (ratio 1: 1 v / v) are added, and the sample solution is observed under polarized light to check the behavior of the liquid crystals of the sample.
The reaction is stopped after 1 min by the addition of water in the ratio 1: 1 v /
v.

The other part (c-wh 4) is heated at 40 ° C. with stirring for 5 minutes.
then are 5 mL of a mixture of 98% acetic anhydride and 100% acetic in a ratio 1: 1 v / v.
Then 61.11% of a 5% catalyst (see above) is added to the mixture ; the reaction is stopped in 1 min by pouring water in a 1: 1 v / v ratio.
Finally, all solutions are subjected to ultracentrifugation (65000 rpm during 15-30min) to collect and rinse the products; electrolytes residuals are removed by ion exchange resin for 3 hours before filtration.

Acetylation with acetic anhydride 98%
10 mL of a 2.4% by weight solution of desulfated cotton whiskers (c-wh is desulfated by 2.5 N HCl for 3 h) are mixed with 90 mL of acetic acid 100%;
the water is removed by means of a rotary evaporator (the temperature of the bath of water obtained is less than 40 C).
a) 4 mL of 98% acetic anhydride is added to 40 mL of the resulting solution after 1 min with stirring, then about 90 mL of water are added (1AA-dc-WH).
b) 12 ml of 98% acetic anhydride are added in 40 ml of solution obtained after 15 minutes with stirring, then about 80 ml of water are added (3AA-dc-WH).
Both samples are washed with water by centrifugation, and stored with a bed of resin for 3h, then filtered.

Staged acetylation using 98% acetic anhydride 5 mL of a 2.4% by weight solution of desulfated cotton whiskers (c-wh is 2.5 N HCl desulfated for 3 h) are mixed with 0.5 mL of acid 98% anhydride, the reaction being maintained for 10 min with stirring; the same procedure is repeated 9 times.
The mixture is then divided into two fractions.
a) a fraction is washed with water by centrifugation and stored with a bed of resin for 3 h, then filtered (fraction STW1) b) the other fraction is stored in the presence of anhydride acid at 4 ° C.
night, rinsed by centrifugation and kept with a bed of resin for 3 hours, then filtered (fraction STW2) Protocol 13: Surface grafting of poly-caprolactone The surface grafting of poly-e-caprolactone is carried out on BON and whiskers of cotton.
50mg of dried whiskers are mixed with 860mg of e-caprolactone 48h.
800mg of poly-ε-caprolactone are then added, and the dispersion is subject to 5x1Osec treatment.
1.5 L of benzyl alcohol is added as co-initiator, then degassed with nitrogen for 30 minutes.

The solution is heated to 95 C; 27 L of Sn (Oct) 2 is added under atmosphere nitrogen.
The polymerization is continued for 18 hours, before redispersion of the product in 2 mL
THF, filtered and rinsed with methanol.

B. Result Result 1: Stabilization of an emulsion by means of nanoparticles of bacterial cellulose The nanocrystals of bacterial cellulose are obtained according to protocol 1, and consist of neutral particles.
As shown below, these nanocrystals have excellent properties for form particularly stable Pickering emulsions.
Such emulsions have been produced according to protocol 8, for different ratios hexadecane / aqueous phase, namely from a 10:90 ratio to a ratio 50:50.
Thus, the particle concentration in the emulsions varies with volume fraction water in said emulsions.
Optical microscopy analysis according to protocol 9 gives the results specified in Table 1 below.

Table 1 Sample number Area Dn average Dw average polydispersity% aggregates (average ratio lm lm hexadecane - drops m2 water) 10-90 250 6.4 3.0 3.4 1.15 95.0 20-80 250 7.9 3.3 3.7 1.12 92.2 30-70 855 13.9 4.3 4.8 1.12 71.3 40-60 252 18.1 4.9 5.5 1.12 65.4 50-50 259 24.0 5.6 6.4 1.14 35.8 Measurements of number of drops, average area, number average diameter (Dn medium), average diameter by weight (average Dw), polydispersity (average Dw /
Medium D) and percentage of aggregates, were measured as described by Putaux et al.
(1999, International Journal of Biological Macromolecules, Vol. 26 (2-3): 145-150) and by Barakat et al. (2007, Biomacromolecules, Vol. 8 (4): 1236-1245).
For these different ratios, approximately the same average diameter is measured by image analysis, namely 42 μm with a polydispersity of 1.13 0.2.
The main difference concerns the rate of aggregation which decreases with the decrease of the amount of particles per mL of hydrophobic phase.
According to these results and in order to limit aggregation phenomena, a ratio of from 30:70 is chosen for the following experiments.
The stability of the samples, preserved under different conditions (time, temperature), is evaluated according to protocol 9.

No variation in droplet size was observed even after the retention samples for one month at 4 C or 40 C, or up to 3 hours at 80 C.

Result 2: Characterization of cellulose nanocrystals The nanocrystals of bacterial cellulose obtained according to the protocols 1 to 5, are characterized by transmission electron microscopy in accordance with protocol 7.
surface characteristics of nanocrystals and the characteristics of the emulsion are determined according to protocols 6 and 9.
The results obtained are summarized in the following Table 2.
Table 2 Sample Length / DS Density of Number of Size of Thickness (sulfate / sugar) charge charge per droplets in nm (sulfate / nm2) nanocrystals (11m) Dnou picture J
BCN 919/17 1.96'10-4 9.68'10-4 42.9 4.3 s-BCN 644/17 2.41 * 10-3 1.19 * 10-2 370.7 6.8 ds-BCN 624/12 5.92'10-4 2.92'10-3 69.8 3.4 Cotton tO 189/13 7.92 .10-3 0.123 952 11.0 Cotton t1h HCI 157/13 2.23 .10-3 0.035 224 6.7 Cotton t2h 147/13 1.21.10-3 0.019 114 3.2 Cotton t5h 141/13 1.24.10-3 0.019 123 3.7 Cotton t1Oh 117/13 1.32.10-3 0.020 100 5.9 Cotton t1Oh TFA 128/13 1.08.10-3 0.017 89 5.3 It is specified that for Table 2, the charge density can be expressed indifferently in e.nm-2 or in sulfate.nm-2, because the sulfate ion carries a single charge.
Electron microscopy analyzes show that particles have all one elongated shape.
For all cellulose nanocrystals, hydrolysis by sulfuric acid has tendency to decrease the length. For example, the BCN is decreased from 919 nm to 644 nm without significant variation in width after the sulfation step.
In contrast, hydrolysis with hydrochloric acid tends to peel the surface of cellulose nanocrystals and so reduce or even eliminate the groups sulfate, and so reduce or eliminate the corresponding charges.
The corresponding emulsion is very stable (at least one year), and resists the freezing and heating (2 hours at 80 C).

Result 3: Influence of the ionic strength on the stability of the emulsions.
Emulsions were prepared from cotton cellulose nanocrystals as described in Protocol 8 For the preparation of emulsions, an aqueous medium having values increasing ionic strength.
More specifically, liquid aqueous media having increasing final concentration of NaCl, as shown in Table 3 below.
Table 3 NaCl (M) Thickness (mm)% by volume Zeta pot (mV) 0.02 9.2 42.6 -35 0.05 9.6 44.4 -25 0.08 9.5 44.0 -10 0.1 9 41.9 -0 0.2 9.08 42.0 ND *
0.5 7.97 36.9 ND
* ND: Not determined The results are presented simultaneously in Table 3 and Figure 1.
The results presented in Table 3 show the evolution of the thickness of the emulsion obtained after creaming (centrifugation); it is a value relative in mm, of a Emulsified volume percentage and zeta potential values that illustrates level screening of surface charges with added NaCl.
The results presented in Figure 1 illustrate even more clearly obtaining a stability of the emulsions of the invention, as soon as the strength value is reached ionic brought by a final NaCl concentration of 20 mM.

Claims (25)

1. Composition in the form of an emulsion comprising a hydrophobic phase dispersed in an aqueous phase, which composition contains particles emulsifiers capable of stabilizing said emulsion, characterized in that some at least said particles consist of shaped cellulose nanocrystals elongated who check the following characteristics: a length of between 25 nm and 1 μm, and a width between 5 and 30 nm. 2. Composition according to claim 1, characterized in that the nanocrystals of cellulose have the following characteristics: a length between 100 nm and 1 μm, and a width of between 5 and 20 nm. 3.- Composition according to any one of claims 1 or 2, characterized in this that the cellulose nanocrystals have a length / width ratio higher than 1 and less than 100, and preferably between 10 and 55. 4. Composition according to any one of claims 1 to 3, characterized in this that cellulose nanocrystals have a density of surface charges maximum of 0.5 e.nm 2, e corresponding to an elementary electric charge. 5. Composition according to claim 4, characterized in that the nanocrystals of cellulose have a charged surface, with a charge density of surface included between 0.01 e.nm-2 and 0.31 e.nm-2. 6. Composition according to claim 5, characterized in that the nanocrystals of cellulose have negative surface charges. 7. Composition according to claim 6, characterized in that the nanocrystals of cellulose have on the surface anionic groups bearing the surface charges. 8. Composition according to claim 7, characterized in that the groups anionic cellulose nanocrystals are selected from the groups sulfonate, carboxylate, phosphate, phosphonate and sulfate. 9. Composition according to claim 4, characterized in that the nanocrystals of have a neutral surface, the density of surface charges being less than or equal to 0.01 e.nm-2. 10. Composition according to any one of claims 1 to 9, characterized in this that said composition has an ionic strength less than a force ionic equivalent to mM NaCl, and in that the cellulose nanocrystals have a density loads maximum area of 0.03 e.nm-2. 11. Composition according to any one of claims 1 to 10, characterized in that that the cellulose nanocrystals have, on the surface, groups hydrophobic. 12. Composition according to claim 11, characterized in that the groups hydrophobic properties of cellulose nanocrystals consist of acetyl. 13. Composition according to any one of Claims 1 to 12, characterized in that it comprises from 0.035% to 2% by weight, preferably from 0.05% to 1% by weight.
weight, from cellulose nanocrystals relative to the total weight of said composition. 14.- Composition according to any one of claims 1 to 13, characterized in that that the hydrophobic phase represents from 5% to 45% by weight relative to the weight total of said composition. 15.- Composition according to any one of claims 1 to 14, characterized in that that the hydrophobic phase is chosen from vegetable oils, oils animal oils minerals, synthetic oils, hydrophobic organic solvents and polymers hydrophobic liquids. 16.- Composition according to any one of claims 1 to 15, characterized in that that the composition is chosen from food compositions, compositions cosmetics, pharmaceutical compositions and compositions Phytosanitary. 17.- Use of cellulose nanocrystals as defined in one of any of Claims 1 to 12 for stabilizing an emulsion comprising a phase hydrophobic dispersed in an aqueous phase. 18. Process for the manufacture of a composition in emulsion form according to Moon any of claims 1 to 16, characterized in that it comprises the following steps :
(a) the supply of cellulose nanocrystals as defined in one of any of claims 1 to 12, then (b) incorporating said cellulose nanocrystals into the aqueous phase of said composition, so as to stabilize said emulsion. 19. A process according to claim 18, characterized in that the nanocrystals of cellulose provided in step (a) are obtained by a process of from a cellulose, said manufacturing process being selected from one of the processes following:
mechanical fractionation, controlled chemical hydrolysis, and dissolution / recrystallization. 20. A process according to claim 19, characterized in that the method of manufacturing cellulose nanocrystals is followed by a post-modification process said cellulose nanocrystals at the end of which their density of surface charges and / or their hydrophobicity are modified. 21. A process according to claim 20, characterized in that the method of post-modification consists of a process for the introduction or hydrolysis of groups carrying the surface charges. 22. The process as claimed in claim 21, characterized in that the operation of post-modification comprises a step of introducing or hydrolyzing groups of surface chosen from sulphonate, carboxylate, phosphate and phosphonate groups and sulfate. 23.- Method according to any one of claims 21 or 22, characterized in that the manufacturing process consists of a mild acid hydrolysis process of cellulose by sulfuric acid, to obtain cellulose nanocrystals provided with sulfate groups in surface area, and in that the optional post-modification method consists of a process controlled hydrolysis of said sulfate groups. 24.- Process according to any one of claims 21 or 22, characterized in that the manufacturing process consists of a mild acid hydrolysis process of cellulose by hydrochloric acid, and in that the optional post-modification process consists of a post-sulfation process of said cellulose nanocrystals. 25. The process as claimed in any one of claims 18 to 24, characterized in that what the cellulose is chosen from at least one of the original celluloses next: vegetable, animal, bacterial, algal or regenerated from a transformed cellulose from sources commercial.